Linda Black Elk, a member of the Standing Rock Medic and Healer Council of the Catawba tribe, said she treated protesters for injuries and hypothermia and that they were soaked by water in temperatures as low as 23 degrees.

— STEPHANIE KEITH / Reuters

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Police stand guard at barricades near the Standing Rock Reservation where thousands have amassed to protest the construction of the pipeline.

— Richard Tsong-Taatarii / Minneapolis Star Tribune via Zuma

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A protester watches the confrontation with police from the sidelines.

— STEPHANIE KEITH / Reuters

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Police use a water cannon to put out a fire started by the protesters.

— STEPHANIE KEITH / Reuters

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A protester gets warm by a fire during the protest.

— STEPHANIE KEITH / Reuters

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An injured protester is given medical attention.

— STEPHANIE KEITH / Reuters

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A rubber bullet and an apparent rubber bullet wound are displayed during the protest.

— STEPHANIE KEITH / Reuters

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Police fire tear gas at protesters.

— STEPHANIE KEITH / Reuters

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A horse gallops through the confrontation between police and protesters.